Field of the Invention
The invention relates to a method and apparatus for isolating a plurality of vertically spaced sets of perforations provided in a well conduit adjacent production formations to permit the concurrent treatment of such formations with predetermined amounts of a treatment fluid, either liquid or gas. In many oil and gas wells, the well conduit may traverse a plurality of vertically spaced production formations or zones. The well conduit is generally perforated to provide communication with each of the production zones. If the need arises for chemical treatment of the production zones, it is highly desirable that each of the set of perforations be isolated from each other so that treatment may be selectively applied to only one or more of the production zones. Similarly, in many oil and gas fields, a plurality of wells located in close proximity to each other traverse common production formations. When the initial production from such wells reach an unacceptably low level, it has been a common practice to perform secondary recovery operations on the wells. The secondary operation comprises taking a centrally located one of a group of wells and applying either water or carbon dioxide to the production zones traversed by such well. Such water or gas flooding drives the hydrocarbons in the production formation towards the remaining active wells and enhances their productivity. In both recovery operations, it is highly desirable that the sup plied fluid be confined to the production zones and thus be capable of substantial recovery from the producing wells. This is particularly important in recovery operations where pressurized carbon dioxide is utilized. Here again, the necessity arises for effectively isolating each set of a plurality of vertically spaced sets of perforations in the well conduit carrying the treatment fluid from the adjoining sets of perforations.
The prior art has not provided a simple, inexpensive method and apparatus for isolating a plurality of sets of perforations in a well conduit from each other so as to permit the selective application of predetermined amounts of treatment or flooding fluid concurrently to each of the sets of perforations.